1. Field of the Invention
The present invention relates to a method of setting and/or actuating a multi-stable valve used in fluidic or in micro fluidic applications. Another object of the invention is an adjustable multi stable valve for use in medical devices implanted in a human body.
More specifically, the invention relates to a micro valve having at least two stable states at operating temperature. An opening pressure and a resistance to fluid flow correspond to each state of the valve. The valve may be actuated non-invasively, by telemetry for example, with an external device, providing an adjustable opening pressure valve or alternatively a valve assembly with adjustable resistance to flow.
2. Discussion of the Related Art
The valve object of the present invention has a wide range of applications in different fields (medical, hydraulics, micro-engineering, etc.). For example, in the medical field related to the treatment of hydrocephalic patients, it is necessary to install a shunt system that derives the excess of liquid from the brain to the peritonea or to another cavity of the patient. Some existing shunt systems comprise an adjustable valve that allows the surgeon to modify non-invasively the valve opening pressure after implantation. These existing implantable valves for the treatment of hydrocephalic patients have successfully shown that the feature allowing the surgeon to adjust non-invasively the valve opening pressure after implantation is extremely useful. Nevertheless, there are some drawbacks associated with devices of this type that can be summarized as follows:
These known implants do not provide the user with any feedback during or after adjustment of the valve opening pressure. Therefore, it might be necessary to take an X-ray for checking the valve setting. Furthermore, the valve can be misadjusted by strong magnetic fields, such as those generated by a permanent magnet found for example in magnetic resonance imaging devices.
Finally the existing valves are sometimes blocked due to an accumulation of bio-substance on the mechanical parts of the valve mechanism.
Some other known electromechanical or pneumatic valves require energy for remaining in one or more working positions and are not suitable for human or animal implantation due to their size and/or their lack of tightness.